Telephone-exchange system



TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED $58.12, i920.

Patented Apr. 5, H2L

2 SHEETS-SHEET l.

'UW Pom/f@ WJ/f/ L. POLNKOWSKY.

TELEPHGNE EXCHANGE SYSTEM.

APPLICATION mit FEB. i2, 1,920.

Patented Apr. 5, 1921i.

2 SHEETS-SHEET 2.

Nomils FEYERS. m0,. Lm1o WASHINGTON. D C.

stares earner editrice.

LIPA POLlNKOlSKY, 0F `ANTlitlR7 BELGIUM, ASSGTNOR T0 WESTERN ELECTRICCOMPANYVNCORPORATED, 0F NEW YORK, N. Y., A CORPORATION OF NE YORK.

TELEFHONE-EXCHANGE SYSTEM.

` ricreare.

Specification of Letters Patent.

resented apr. s, reci.

To all w hom t may concern."

Be it'lrnown that l, Liri-r Porinirowsirr, a citizen of Russia, residingat Antwerp, Belgium, have invented certain new and useful improvementsin rTelephone-Exchange Systems, oi" which the following is a full,clear, concise, and exact description.

This invention relates to telephone exchange systems and particularly tosystems employing selectively operable Aswitching devices forestablishing talking connections between subscribers lines.

rlhe object or this invention is the provision. ot a switch controllingmechanism comprising a register arranged to respond to a plurality oiseries of impulses ifor determining the selection and operation of theautomatic switches used in establishing con- 'nections A. feature of theinvention relates to a switch controlling mechanism in which a registeris positioned responsive to a series of impulses to select one otaplurality oi automatic switches, and is then again positionedresponsive to a succeeding seriesof impulses td control the selectiveoperation of such automatic switch.

Further features of the present invention will become obvious from thefollowing description and appended claims. i

ln the drawings, Figures 1 and 2, taken in ordei, illustrate a portionof a telephone system embodying thev invention. `Figl discloses twosubscribers lines together with a pair einen-numerical or finderswitches 'flier extending these lines. Fig. 2 shows two selectiveswitchesv joined by means et a linlr circuit with the finder switches inFig. l and which serve to complete the extension of calling lines to thelines of called subscribers. There is also shown in Fig. 2 a switchcontrolling mechanism comprising a register for determining theselection and operation ofthe selective switches. f V

The present invention is particularly applicable te small privatebranchexchange systems of therull automatic type where only a comparativelyfew selective operations` are necessary for the establishment of talkingconnections. It will `be understood, however, that the invention is notlimited to either small capacity systemsk or to systems of the full'automatic type; In

, the disclosure there is shown a switching yarrangement adapted toaccommodate a private branch exchange having twenty subscribers lines.These lines are arranged in two groups of ten lines each. All the linesin the first group, such as line 200, appear as callinglines in themultiple contacts oi line finder switches, such as the switch 210. Alllines in the second group, such as line 205, appearin the multiplecontacts of'line finder switches, such as switch 220. The lindcrswitches 210 and 220 comprise a line linding unit arranged to extend anyone of the twenty lines to a link circuit 202, 203 and 206. For thispurpose the contacts of finder `switch 210, such as contacts 216, 217and 216 and the contacts of finder v220 such contacts 225, 226 and 227are connected to the corresponding conductors 202, 203'y andk .206 ofthe link circuit. When a call is initiated in the first group of tenlines the switch 210 is automatically operatedy to vselect the callingline and extend it toa the thereupon automatically 'selects thecalling'f line and extends it to the 203 and r206. Y

rlhe link circuits extending trom the contacts of the line iinderwitches, terminate link circuit 202,

in contacts such 284.-', 285 and 286 of the connecting unit. rlhe switch280 serves to complete connections to one of the groups of tensubscribers lines and switch 290 serves to complete connections to theother 4group often lines..v ln additionto this, two

positions of the switch 290 are reserved for the completion etconnections to trunlrlines Vleading from the private branch exchange tothe central oilice.

lin manner similar to thearrange-` A switch controllingmechanismcomprisi ing a multi-position register is provided for selecting one orthe other of theswitches 280 and 290 and also for controlling theoperation oit the selected switch to complete the connection to thecalled line.

broken line are `controlled by switch 290, the

contacts between the two` vertical broken lines are controlled by switch280, the contacts within `the small broken rectangle in-v closingregister 100 are controlled by such register and the reinaining switchcontacts are controlled by the sequence switch 250.l

ltis believed that a clearer understanding is to be had of the inventionby describing in detail the establishment and release of a telephoneconnection. For this purpose it is iirst assumed that the subscriber ofline 200 in the iirst group of ten lines desires to converse with thesubscriber oi' line 208, which is also located inthe iirst group of tenlines. For convenience the lirst group of ten lines is numberedconsecutively from 10 to 19 and thev second group of lines is numberedconsecutively from 20 to 29. Hence, the iirst, or tens digit of alllines in the iirst group is 1 and the first digit of all lines Vin thesecond group is 2. Upon renioving the receiver from the switchhook thesubscriber of line 200 closes a circuit inroin battery through thewinding of coinmon start relay 20st, left-hand winding of line `relay201, contact and innerI armature oiE cut-oli2 relay 207, over the loopof the calling line to ground at the outer armature and contact of relay207. Relay 201 attracts its armature and closes a pathi'rorn batterythrough the winding ci relay 207, right-hand winding and Contact andarinature of relay 201 tothe contact 218 of the Vline iinder switch 200.Relay 20eA by energizing closes a circuit from ground through itscontact and armature, conductor 211, Contact 243 (1) of sequence switch250,

Aarmature and Contact ofrelay 268, winding of slow-toenergize relay 233to batteryA and ground. A parallel branch of this circuit also closed byway of the armature and and ,establishes the following circuit foroperating the line finder switchl 210; batV .tact 213 to ground.

contact 238 (1), contact and armature of relay 233, conductor 222,contact 223, con- The finder switch 210 startsl troni whatever positionit happens to be standing in and commences to rotate in search of thecalling line. ris the finder switch 210 passes through each of its haltpositions the upper contact 213 is closed to ground. @n reachingposition 111i the above traced path :troni battery through the wind# ingof cut-oit relay 207 to contact 218 is completed by way of conductor206, contact 2416 (1), lett-hand winding. of test relay 264, conductor215, contact 213 to ground, rlhe contact 218 is -so arranged that it isclosed in its successive positions simultaneously with closure oi'contacts 213 in theco "responding half positions. Hence, as theiinderswitch approaches,position 2 the circuit just traced iseonipleted andre- .lay 207 becomes energized. Relay 264i energizes in the circuitincluding its lett-hand high resistance winding and completes a holdingcircuit through its right-hand low resistance winding and front contactand `armature for cut-oil relay 207 and line relay 201. This lowresistancecircuit to ground` reduces the potential on contact 218 to render the line busy. Relay 264i at its back contac` opens the above tracedvcircuit for the'energization oi' relay 239. Relay 239retracts itsarmature and coinpletes a circuit from battery through the winding ofsequence switch 250, contact 2410 (1), back contact and armature ofrelay 239, contact 238 (1), Contact andarniature ofrelay 233, conductor222, contact 223, contact 213 (2) l to ground.' Sequence switch 250advances from position 1 to position 3. lt will be observed Vthat theAcircuit traced from sequence switch 250 depends upon the front contactand armature of relay 233. The ciicuit Voit this relayis Vopened at thearmature and contact of relay 204i as soon as the cut-oil relay 207 isoperated to open the circuit Voi' said relay 204a Relay 233, however,be-

ing slow to denergize does not release its armature until after relay239 has had time to denergize and complete the circuit for movingsequence switch 250 into position 3. 0n reaching position 2 sequenceswitch 250 closes a direct circuit to ground atcontact 219 forniaintaininwr theieneroization of rel lay 207 and relay 201. rThe iinderswitch 210is 'thus brought to rest on the contacts of the calling line200, tlieopcrating circuit of'said Vswitch being opened by thedenergization of relay 239.

In position 3 oit the .sequence switch 250 theriinpulse relay 231 isenergized in series with the calling'line'zby Ineans of a circuit'numerals from Oto 9.

and back contact of relay 239, contact 24rd (3), left-hand winding otrelay 239 winding oit i'egistei'100 to battery and ground. A circuit isalso closed ytroni battery through the right-hand winding of relay 239,contact'2a1 (3), front contactand armature ot relay 231vr to ground atcontact 243. Relay 239, being` differential, does not operate when bothof its windings are energized simultaneously. "Ehe register 100,however, becomes energized in series with the left-hand winding oitrelay 239 and moves out of position O. Between position and position 1the master contact "101 01"' register 100 closes a direct circuit togroundY in shunt oft the left-hand winding otdiiierential; relay 239.The current flowing in the right-hand winding ot relay 239 is nowsuilicient to energize said relay. rlhe register 100 under the controlof its master` contact continues to move into position 1.

lt may bewell to explain this point that the register `10() isprovidedwith ten controlling positions, one foreach of rthe rlhis register`responds-to the series of impulses sentftrom the calling subscribersdial vand advances into a position corresponding vto the number ofimpulses contained in the series. K rllhe register having assumed lacertain position, dependent upon Vthe number of' impulses transmitted,later runs through the remainot its ten positionsto,` normal to controlthe selection and operation oi the selective switches 280aiid 290. `ltwill be seen, thereiitore, that the number ot positions passed throughby the register in reaching its norinal position is the complement ofthe number of impulses sent 'trom the calling subsci'ibei"s dialv tovset theregister. ln order that the switches maybe controlled inaccordance withftlie rdi its ot called numbers 'as listed in thediictory, it is oiilynecessary to variraiiigge themsiibscribers dialssuch that seriesfot inipuses corresponding tothe complements rather'than'fto the actual" l` gits themselves are transiiii'tted to theregister.V The'. subscribers dialsv are furtherl arranged such that thelast interruption ot the liney in eachimpulse series is comparativelylonger than preceding interruptions. The purpose r-'eXplain`ed, toposition 1, nothing further occurs until the subscriber commences toSend impulses.,l In position`3 oi' sequence switch 250e. circuit isclosed froml battery through thev right-hand winding ot' tone coil 242,contact 276 interrupter 247 to ground. Current flowing iii this circuitproduces a .characteristic sound in the receiverat the callingsubstation to advise the calling subscriber that the apparatus is incondition to receive impulses. The calling subscriber thereuponmanipulates his dial 228 to send the tens series of impulsescorresi'aonding to the first digit 'ot the called number. Since thecalled line belongs to the firstN group, the tens digit is 1 andconsequently the tens series comprises nine impulses. When the callingline is opened for the first impulse, relay 231 .denergizes The releaseof relay 231opens the circuit for the right-hand winding of`differential relay 239, which` in turn denergizcs. On the next closureof. the line'circuit at the completion ofthe first impulse, the abovetraced circuit is established for register 100. This register' advancesfrom positionV 1 into position 2, and the relay 239 is energized, asabove eX- plained. At thecompletion of the second impulse, relay 239denergizes and the register 100 advances into its next. position.

This method ot operation continues until the last impulsev of the'series istransmitted, yat which time register 100 will have reachedVposition 9. Duringeach brief interruption of the circuit of krelay 231,a circuit is completed from battery through the windings of relay 234,resistaiice212, back contact and armature of relay 231, contact 241s (3)to ground. The relay 2311 being slow to Venergize does not Vattract itsarmature in response'to the short closures ot-liis circuit.

-At the last' impulse of the series, however, `relay. 231 vremainsde'cnergized for a suiiiclosed from battery through the right-hand'winding of relay .239, Contact 241g. (6), bach contact'ancl' armature,of relay 264C to ground. Relay 239 becomes energizedanil closes aycircuit from batteryjthroughf the winding of register 100, Vcontact 102,conta/:t

(6), front contact and armature of rc- `ylay 239,'front Contact andarmature 'ot relay sterv 100 Veiiieigizes in this circuit ,and advancesfrom position 9 to its normaly position l0.v

231, contact 243'r to ground.`

lt is not necessary to maintain .sequence 100"will,have suiiicient timeto advance switch 250 in position 6 since the register i from either ofits positions 8 or 9 to its normal position during the period 4thatsequence switch 250 is passing through position 6. Consequently whensequence switch 250 reaches yposition 6 a circuit is closed from batterythrough the winding of said sequence switch, contact 255v (6 to 7), backcontact and armature of relay 234, contact 235 to ground. Sequenceswitch 250 thereupon advances over position 6 and position 7 intoposition 9. In passing out of position 6, contacts 244 and245 open thecircuit ofthe impulse relay 231. This circuit is 'again energized uponsequence switch 250 Vreaching position 3, and relay 231 isincluded inseries with the calling line.

With the sequenceswitch 250 in position 9 and relay 231 energized, acircuit is coinpleted frombattery through the winding of register 100,left-hand winding ot relay 239, contact 240 (8 to 9), backcontactandarmature of relay 239, front contact and armature of relay 231,'contact243 to ground. At the same time the above tra-ced circuit for theright-hand winding of differential relay 239 is closed to ground atcontact 243. The register 100 energizes in the above circuit andadvances from position 0 into position 1. The calling subscriber nowoperates his dial in accordance with the units digit.

`The register 100. isiadvanced from position to position, as described,in response to the units series of impulses. On thelast `coniparativelylonginterruption of the line, relay 234 attracts its armature and closesva circuit from battery through the winding of sequence switch 250,contact 253 (9), front contact and armature ofrelay 234, contact 235 toground. ASequence switch 250 moves out of position 9 and into position10. After relay 234 has become denergized in position 10 of sequenceswitch 250, a circuit is closed from the winding ofv said sequenceswitch, contact 255 (10), back contact and armature of relay 234,contact 235 to ground.` Sequence switch 250 thereupon advances from'position 10 into position 11. In position 11 of sequence switch 250 theselective switch 290, having access to the group of lines containing thecalled line isstarted in operation. The circuit for operating thisswitch may be traced f trom :battery through the winding of the magnetof said switch, back contact and right-hand armature of relay 274, backcontact and armature of relay 262, contact 255 (11), back Contact' andarmaturev of relay 234, contact 235 to ground. Switch 290 movesffromposition 1 over positions 2, l3 ancl'4 and into position 5, positions 2and 4 being reserved as above noted for central office connections.VInpassing position 4,3,

contact 293 is closed to complete'a circuit from battery through thewindinglof register 100, contact 102, contact 293 (41,), contact 283closed in position 1, contact 254 (11)baclr'contact and armature ofrelay 264 to ground. The register 100 energizes in this circuit andmoves forward one position. and-in each oi its half positions thecontact 293 is closed to advance the register 100 one position. Thisprocedure continues until register 100 has been fully restored to itsnormal position 0. ln position 0 of register 100 a circuit is closedfrombattery through the winding of relay 234, conductor 229, Contact 104(0), contact 256 (11) to ground. Relay 234 attracts .its armature andcoinpletes a circuit from battery through the windingof sequence switch250, contact 253 (11), front contact and armature of relay 234,` contact235 to ground. By means of this circuit the sequence switch 250 movesout of position 11 and.` into position 13.

The selectivel switch 290 is now in the proper position to close thelink circuit through Vto the called line by way of contacts'294, 295 and296. tWhile sequence switch 250 is passing through position 12, a testis made to determine the busy or idle position of the called line 203.The circuit for performing this test may be traced from ground, contact256 (12), left-hand high resistance winding of test relay 264, contact246 (4 to 16), conductor 232, contact 296,

237, and relay 261 becomes energized byV means of itshigh resistancewinding. Relay 261 attracts its armature and completes a substitutecircuit to ground through its right-hand low resistance winding. Thislow resistance path decreases the potential on the test conductor 237ofthe called line to render this line non-selectable by other switches.In position 13 of sequence switch 250 a circuit is closed from battery.through the winding of said sequence switch, contact 240 (13), baclrcontact and armature of relay 239,'front contact and armature of relay231, contact 243 to ground. The sequence 'switch 250 moves Jfromposition 13 into position'15.

VTn position 15 of sequenceswitch 250 ringing current is applied to the,called line by means of the following circuit: ringing source 251,contact 266 (15), contact 295 of switch 290, over the lower conductor ofthe called line 208 and returning by way of The switch 290 continues toiotate.

izo

the upper conductor of the called line to conate in series with the bellat the calledV substation. When the called subscribed removes hisyreceiver `from the switchhook, the re- Y tact 294 of switch 290, contact265 (15) consistance ol' the called line loop is reduced, as is wellunderstood, to permit the energization oi relay 234. Relay 234 completesa circuit from battery through the winding of sequence switch 250,contact 253 (15), 'liront contact and armature of relay 234, contact toground. Sequence switch 250 advances from position 15 into position 16.Position 16 of sequence switch 250 is the talking position. Battery issupplied to the calling line through the winding of relay 231 and to thecalled-line throughl the windings of relay 262 and contacts 265 and 266.

After conversation has been completed and the calling' subscriber hangsup his receiver, the supervisory relay 263 is deencrgized. A. circuitthen completed from battery through the winding of relay 233, contactand armature or relay 268, contact 243 to ground. Relay attracts itsarmature and -closes a circuit from battery through the winding ofsequence switch 250, contact 253 (16), contact and armature of relay233, conductor 222, contact 223, contact 13 to ground. Sequence switch250 advances into position 17.. @n leaving position 16 sequence switch250 opens at contact' 219 the holding circuit for the line relay 201 andcut-off relay 207. rthese relays become denergized to permit theinitiation of iiurther calls by the subscriber of line 200. lVithsequence switch 250 in position 17 and the called line relay 262denergized, a circuit is closed as follows for the restoration oi' theselective switch 290 to its normal position: battery through the windingof the magnet switch 290, back contact and right-hand armature of relay274, back contact and armature or" relay 262, contact 238 (17), contactand armature or relay 233, conductor 222, contacts 223 and 213 toground. IThe switch 290 rotates back to its normal position. As theswitch 290 reaches position 18 a circuit is closed from battery throughthe right-hand winding of relay 262, contact 105 (0) of register 100,contact 293 (18), contact 283 of switch 280, contact 254 (17), baclrcontact and armature or' relay 264 to ground. Relay 262 attracts itsarmature to openthe driving circuit of the selective switch 290. Thisswitch, Vhowever, under the control or its master contact advances intoposition 1. Vlllhen relay 262 attracts its armature a circuit isestablished irom battery through the winding of sequence switch 250,front contact and armature of relay 262, contact 238 (17), contact andarmature of relay 233, conductor 222, contacts 223 and 213 to ground.'Sequence switch 250 advances into position 1, in which position relays262 and 233 are released.

lf the called line 208 is busy at the time sequence switch 250 passesthrough position 250 a circuit is closed from ground through theinterrupter 257, contact 276 (13), righthand winding or tone coil 243 tobattery and ground. The interrupter 257 causes the impression oiE acharacteristic tone on the calling line to notify the calling subscriberthat the called line is already busy. The calling subscriber thenreplaces his receiver ,to the switchhcok and relay 263 becomesdenergized. rllie denergization of relay 268 causes the energization ofrelay k233 in the manner `alcove described. The selective switch 290 isthereupon restored to its normal position by means of the circuit abovetraced, including the back contacts and armatures ofrelays 274 and 262and contact 238v (13). Whenswitch 290 reaches position 18, relay 262becomes energized as described and closes a circuit from' batterythrough the winding of sequence switch 250, front contact andl armatureof relay 262, contact 238- (13), contact and armature of relay 233,conductor 222, contacts 223 and 213 to ground. Sequence switch 250advances 'from position 13 into position 15. Since the callingsubscriber has replaced his receiver to the switchhook, relay 231 isdeenergized and the following circuit is closed for the energization ofrelay' 234: battery through the winding of said relay, resistance 212,baclr contact and armature of relay 231, contact 243 f (15) to ground.Relay 234 completes a circuit from battery through the winding ofsequence switch 250, contact 253 (15) `iront contact and armature orrelay 234, Contact 235 to ground. Sequence switch switch 250, frontcontact and armature of` relay 262, Contact 238 (17), Jiront contact andarmature of relay 243, and thence to ground by way of conductor 222 andcontacts 223 and 213. thereupon moves into its normal position 1.

Sequence switch 250 The case will now be considered in which it isdesired to extend a connection to a subscribers line belonging to thesecond group of ten lines. These lines are selected` by means of switch280 and appear accordingly in contacts, such as 234, 285 and 286 ofswitch 280. To illustrate the operation of the line fin der switch 220,it will be 'further considered in connection with this call that thecalling subscriber belongs to the second group of ten lines, one ofwhich lines is shown at 205. The ten lines of the second group appear ascalling lines in the contacts ot'tinder switch 220, such as contacts225, 226 and 227. Upon the removal of the receiver from the switchhook,the line relay 260, individual to the calling line 205,`is operated inseries with the common start relay 204. Relay 204 operates in the manneralready described to start the line finder switch 210 in rotation. Sincethe calling line 205 does not appear in the contacts'o the first linevfinder switch 210, this switch will continue to rotate until it reachesposition 12. In passing through position' 11, switch 210 shifts thedriving circuit from the first line finder 210 to the secondline finder220. This circuit maynow be traced from ground through the contact 213(10 to 12), contact 223 (1), conductor 222, armature and Contact ofrelay 233, contact 238 (1), armature and front contact of relay239,'contact 249 (1), conductor 221, contact 224, (1), Contact 214 (11),winding of the magnet of switch 220 to battery and ground. rhe magnet ofswitch 220 is energized in this circuit and moves out of position 1. Thefinder switch 220 continues to rotate until it reaches thepositioncorresponding to the callingline 205 of the second group.circuit is then closed from battery through the winding of cutoff relay261, right-hand winding and contact and armature of relay 260, contact227, conductor 206, left-hand winding of test relay 264, conductor 215,coifitact 223 closed in .its off position, contact 2113 (12) to ground.Relay 264 energizesas above described, the finder switch 220 is broughtto rest in engagement with the calling lin-e and sequence switch 250 is'moved into position 3 ready for the transmission of the tens series ofimpulses.

Since the called line belongs to the second group, the tens digitthereof is 2. Accordingly the calling subscriber transmits a series ofeight impulses to set the register 100 in position 8. Sequence switch250 then moves from position 3 vover positions 6 and 7 and into position9, `as described. In passing through positions 4 and 5 'sequence switch250 closes a circuit for the energization or" relay 274 which serves todetermine the selection of the proper one of the two se lectivo switches230and '290. This circuit may be traced from battery through the windingof relay 274, contact 282, contact 106' (8) of register 100, contact 254(4 to 5), back contact and armature of relay 264 to ground. Relay 274becomes energized and locks up over a circuit from battery through thewinding or said relay, Contact 282, lefthand'armature and contact ofrelay 274 to ground at contact 235 (3 to 17). The sequence switch 250 inpassing through position 6 causes the restoration of register 100, asabove explained.

In position 9 of sequence switch 250, th iuiitsimpulses fare sent andregister 100 is advanced to its second controlling position.

After register 100 has been positioned the sequence switch 250 advancesinto position 11. ln position 11 a circuit is closed Jror the operationot the selective switch 280, which advances under the control of theregister 100 to select the terminals ot the called subscribei"s line.This circuit leads from battery through the winding of the magnet ofswitch 280, front contact and right-hand armature ofV relay 274, backcontact and armature of relay 262, contact 255 (11), back contact'- andarmature of relay 234, contact 235 to ground. Each time the switch 28()passes through one of its half positions contact 233 is closed. Acircuit is established from battery through the winding of register 100,contact 102, contact 283, contact 254 (11), bach contact and armature ofrelay 264 to ground. Register 100 rotates from position to position instep with the switch 230 until itis restored to normal. ln position 0 ofthe register 100 a circuit is 'completed from battery through the wind-.ings of relay 234, Contact 104 (0), contact 256 (11) to ground. Relay234 operates and completes circuit from battery through the winding ofsequence switch 250,` contact 253 (11), front contact and armature ofrelay 234, Contact to ground. Sequence switch 250 advances from position11 to position 13. From' this point on the operation involved in thocompletion of the connection is the saine as that already described.

lVhen the subscribers have replaced their receivers to the switchhoolsafter the completion of conversation, relays 263 and 262 becomedenergiiaed and relay 233 becomes energized. Sequence switch 250 isdriven into position 17 bymeans or" 'a circuit from battery through thewinding of said sequence switch, Contact 253 (16), contact and armatureYof relay 233, conductor 222, contact 223, contact 213 (12) to ground. lnposition 17 of sequence switch 250 a circuit is closed Afrom batterythrough the magnet of switch 280, front contactand right-hand armatureof relay 274, back Contact and armature of relay 262, contact 233 (17),contact and armature of relay 233, conductor 222,` contac-ts 223 and 213to ground. The switch 280 rotates back to its normal position, at whichtime a circuit is closed from battery through the right-hand winding ofrelay 262, Contact 105 (0), contact 293 (l), contact 283 (18 to 1),contact 254 (17) back contact and armature of relay 264 to ground. Relay262 encrgizes in this circuit and completes a cir-v cuit from batterythroughv the winding of sequence switch 250, front contact and aimatureci relay 262, contact 238 (17), and thence to ground at contact 213.Sequence switch 250, therefore, advances into its normal position 1.

The next time the finder switches 210 and 220 are taken for use, theswitch 220 is iirst driven to its normal position 1 from the position inwhich it was left in connection with the last call.` W ith linder 220restored to its normal position, the finder 210 isy then started inoperation in the manner described to find the calling line, providedsuch line is one of the lirst group of' lines. 1i the calling line,however, belongs to the second group, finder 210 iirst maires a completerevolution to position 12, whereupon the finder 220 again is set inoperation to ind the calling line in the second group. The circuit forrestoring the linder switch 220 to its normal position may be tracedfrom battery through the winding or the magnet ot' said finder, contact224 (2 to 11), conductor 221, contact 249 (l), front contact andarmature of relay 239, contact 238 (1), contact and armature of relay233, conductor 222, contact 223, contact 213 (12) to ground.

Ars hereinbeiore stated, positions 2 and 4 of the selective switch 290are reserved for central office connections. Two trunks 270 and 271leading to the central otiice are shown as connected to contacts 297,298 and 299 of switch 290 in positions 2 and 4 re spectively. 1n orderto make a central ofi-ice, the calling subscriber operates his dial totransmit ten impulses. ln response to this ,series of impulses theregister 100 makes a complete revolution and stops in position 0. When,therefore, the sequence switch 250 passes through positions 4 and 5 inthe manner explained, a circuit is completed from battery through thewindinO o1' the magnet of switch 290, contact 103 0), contact 254 (4 to5), baclr Contact and armature of relay 264 to ground. The switch 290advances into position 2 where the central oiiice trunk 270 is tested.rThe` test circuitrfor this purpose may be traced from the testconductor 272, contact 299 (2), conductor 232, contact 246 (4 to 16),through the left-hand winding oi' test relay 264, contact 256 (7) toground. The sequence switch 250 will have moved over position 6 and intoposition 7 in the manner hereinbefore described. lf trunk 270 is foundidle, relay 264 energizes. Relay 264 including its right-hand windingand the test circuit reduces the potential on test conductor 272 inorder to render the trunk busy to other switches.,A `When the sequenceswitch 250 passes through position 6 relay 234 energizes in a circuittrom battery through the windings or saidy relay, conductor 229, contact104L (0), contact 2.56 (6) to ground. Relay 234 remains locked up inposition 7 of sequence switch 250 by means of a circuit from batterythrough the windings of said relay, resistance 212, contact 236 (7),iront contact and armature of relay to ground at contact 235. Thecalling subscribers line is connected through to the central or'iicetrunk 270 withsequence switch contacts 244 and 245 closed in position 7,and the further extension of the call may be made in the usual manner.

At the completion of conversation the calling subscriber by replacinghis receiver on the switchhook causes the decneigization of supervisoryrelay 26S., Relay 233 there'v upon energizes by means of a circuit frombattery through the windings of said relay, contact and armature ofrelay 268, armature and back contact of relay 231, contact 236 (7),front contact and armature oiE relay 234 contact 235 to ground. Relay233 com- Jletes a circuit from batter through the winding ofsequenceswitch 250, contact 253 (7), contact and armature of relay 233,conductor 222, and thence to ground at contact 213. Sequence switch 2.30moves into position 9. ln position. 9 of sequence switch 250 relay 234is energized by means of a circuit from battery through the windings oisaid relay, resistance 212,'back Contact andarmature of' relay 231,contact 243 .to ground. Relay 234 completes a circuitrom battery throughthe winding of sequence switch 250,

contact`253 (9), front contact and armature of relay 234 to ground atcontact 235. Se quence switch 250 moves out of position 9 and intoposition 10. 1n position 10 of sequence switch 250 a circuit iscompleted from battery through the winding o1 the magnet of switch 290,back contact and right-hand armature of relay 274, back contact andarmature of relay '262, contact 233 (10), contact and armature of relayy233 to lground at contact 213. Switch 290 restores to its normalposition, at which time relay 262 is energized in the manner abovedescribed. Relay 262 by attracting its ar-` mature closes a circuit frombattery through the windingo'f sequence switch 250, front contact andarmature of relay 262, contact 238 (10), contact and armature of relay233, and thence to ground at Contact 213. Sequence switch 250 thereuponadvances into position 11. Inthis position a circuit is closed frombattery through the winding of sequence switch 250, contact 253 (11),front contact and armature of relay 234 to ground at contact 235.Sequence switch 250 moves from position 11 into position 13. 1inposition 13 of sequence switch 250 relay 262 is energized in a circuitfrom battery through the right-hand winding of said relay, contact 105(O), contact 293 (1), contact 283 (l), contact 254 (13), back contactand armature of relay 264e to ground. Relay 262 closes a circuit frombattery through the winding of sequence switch 250, front contact andarmature oi' relay 262, contact 238 (13), contact and armature ofrelayv233, and thence to ground at contact 213. Sequence switch 250moves into position 15 where a circuit is closed from battery throughthe winding o'i sequence switch 250, contact 253 (15), iront contact andarmature of relay 23a to ground at contact 235. Sequence switch 250advances into position 16. In this position ot sequence switch 250 acircuit is completed from battery through the winding ot said sequenceswitch, contact 2523 (10), contact and armature of relay 233 to groundat contact 213. Sequence switch 25() thereupon moves into position 17. nthis position relay 262 is energized in the circuit above traced andcompletes the circuit already described for driving sequence switch 25()into its normal position.

What'is claimed is: i

1. ln a telephone system, a plurality of selective switches `forestablishing telephone connections, a multi-position register, means forsending series ot' current impulses, impulse mechanism responsive to oneof said series oi impulses tor variably setting said register, meanscontrolled by said register when in its set position Jior selecting oneof said switches, said impulse mechanism being responsive to anotherseries of impulses for again setting said register, and means controlledby said register in accordance with its subsequent setting for operatingthe selected switch.

2. ln a telephone system, a plurality of selective switches forestablishing telephone connections, a multi-position register,means forsending series of currentimpulses, impulse mechanism responsive to oneof said series of impulses for variably setting said register, meanscontrolled by said register when in its set position for selecting oneof said switches, means for thereupon re storing the register to itsnormal position, Said impulse mechanism being responsive to another ofsaid series of impulses for again setting said register, and meanscontrolled by saidregister in accordance with its subsequent setting foroperating the selected switch.

3. In a telephone system, subscribers lines, selective switches forinterconnecting said lines, a multi-position register, means for sendingseries ot' impulses over said lines,

series or impulses for variably setting said register, means controlledby said register when in its set position for selecting one of saidSwitches, said impulse mechanism being responsive to another series or'impulses for again setting said register, and means controlled by saidregister in accordance with its subsequent setting for operat ing theselective switch.

4E. In a telephone system, subscribers lines, selective switches torinterconnecting said lines, a multi-position register', means forassociating said register with a subscribers line, means for sendingseries of impulses over said line, impulse mechanism responsive to oneof said series 'of' impulses for varia bly` setting said register, meanscontrolled by'said register when in its set position for selecting oneof Said switches, said impulse mechanism being responsive to another ofsaid series of impulses for again setting said register, and meanscontrolled by said register in accordance `with its subsequent set tingfor operating the selective switch.

5. In a telephone system, subscribers lines arranged in groups,aplurality oi? selective switches one individual to each of said groupsfor interconnecting the subscribers lines, a multi-position register,means for as- Vsociating said register with a subscribers LIPAPOLINKOVVSKY.

impulse mechanism responsive to one oiv said y

